Process for producing indenes



Nnv. 21, 1950 W. E. ELWELL PROCESS FOR PRODUCING INDENES Filed July 1, 1948 swam tom mwpmawww 3% awn/1,

Under these operating conditions, a conversion of about 15 to 35% f the ethyl toluene or ethyl xylene to either vinyl compounds or indenes occurs in each pass through the dehydrogenation apparatus. The higher temperatures of operation yield the higher ratio of indenes to vinyl xylene production.

From the dehydrogenator 2 the unreacted ma.- terial and the produced products are passed through a heat exchanger 4 into a still 5. In the cooler 4 the product of the dehydrogenator 2 is rapidly cooled to a low temperature such as 50 C. in order to inhibit polymerization of the vinyl material present. In the still 5 the entering material is subjected to distillation under vacuum assisted by steam, and thus distillation is carried out while the material in the still is maintained saturated with an inhibitor of polymerization, such as sulphur. A temperature of distillation in the still of around 75 to 90 C. is maintained while steam is introduced as by a line 6 in the ratio of 2 to 5 parts by weight of steam to 1 part of hydrocarbon material undergoing distillation, in order to vaporize and remove the unreacted ethyl toluene or ethyl xylene. The still 5 will require about 60 to 90 plates in the separating column where ethyl xylene is feed material, in order to efiect the desired separation of the unreacted ethyl xylene from the produced vinyl compound and indenes. The distillation column should be maintained under vacuum corresponding to about to 50 mm. Hg at the top of the column in order to be able to efiect the desired vaporization at a temperature of 75 to 90 C.

In order to prevent polymerization of the vinyl compound in this operation, the distillation system should be maintained saturated with sulphur, for which purpose I have indicated a saturator 1 which should contain sulphur. In the process a part of the ethyl xylene should be recirculated by line 8 through the sulphur saturator 1 and back into the column of the distillation still 5 in order to maintain the contents therein saturated with sulphur. The unreacted ethyl xylene which is separated from the top of the still 5 is recycled by lines 9 and H] to dehydrogenator 2.

From the still 5 the vinyl compounds and indenes, and any tar products in the process, are passed through line H into a second distillation separation still I2 wherein it is again subjected to distillation under vacuum and by the aid of steam in order to vaporize and remove from the system the vinyl xylene product which is removed through line H; and recycled through line I0 to the dehydrogenator 2. The same conditions of operation, except for the control of the refluxing, are maintained in still 12 as are maintained in the still 5, that is, about 75 to 90 temperature and a pressure at the top of about 20 to 50 mm. Hg absolute. The separation of vinyl xylenes from the produced methyl indene is extremely difficult, if not impossible, to efiect in the distillation unit I2, so that it generally is necessary where a pure indene product is desired to allow a return with the vinyl xylene recycled through lines I3 and ID of some of the methyl indene produced. From the bottom of the distillation unit I2, however, a product containing the methyl indenes or other indenes is withdrawn, which may contain some tar produced in the process, but which product is substantially free of the vinyl compounds. This indene product containing tar is passed through line [4 into a further distillation still and column l5, from which the desired indene material is withdrawn 4 as an overhead through line l6, and any tar produced is drawn through line H.

In certain cases it is desirable to produce a product consisting of a mixture of vinyl and indene compounds. In such a case, rather than recycling the mixture of vinyl and indene compounds to the dehydrogenator through line l3, such mixture may be withdrawn as a useful product. Also, in certain cases the vinyl column 15 may be omitted and the entire vinyl and indene compounds produced in the process withdrawn as an overhead from column l2 and passed from line 13 to storage.

In the process the recycled vinyl material undergoes further dehydrogenation in a dehydrogenator 2 into the indene product. Under certain circumstances, of course, one may operate the process so as to produce two products, i. e. a vinyl toluene or xylene and an indene or methyl indene, in which case the vinyl material would not be recycled to the dehydrogenator.

As illustrative of the operation of the process of the present invention: In one example of the process 2,5-dimethyl l-ethyl benzene was the feed product and the chromium oxide type of catalyst was utilized. The space rate in the dehydrogenation zone was maintained at about three volumes of ethyl xylene per volume of catalyst per hour, and the chromium oxide type of catalyst was employed, A temperature of operation was maintained constant during each of three runs. The temperatures of operation in the successful runs were 1040 F., 1068 F., and 1120 F. respectively. The product withdrawn from line 3 analyzed in the three respective cases 20.1%, 20.9%, and 24.8% vinyl xylenes, and 2.2%, 2.9%, and 5.2% methyl indenes. This illustrates that the higher operating temperatures are favorable to the maximum conversion to methyl indenes.

In another test operation of the Process, using the same catalyst, space rate, pressure of operation, the feed material consisted of 65% of the 2,4-dimethyl l-ethyl benzene, 25% of the 2,6-dimethyl l-ethyl benzene, and 10% of the 3,5-dimethyl l-ethyl benzene. Test operations at the respective temperatures of 1031 F., 1067 F., and 1118 F. were maintained, The product from the dehydrogenator in this case analyzed respectively 18.5%, 18.6%, and 21.2% vinyl xylenes and respectively 3.2%, 4.8%, and 6.9% methyl indenes.

While the particular example of the process herein described is well adapted to carry out the objects of the invention, various modifications may be made, and this invention is of the scope set forth in the appended claims.

I claim:

1. A process of producing indenes and methyl homologs thereof, by catalytic dehydrogenation which process comprises subjecting a member of the group consisting of ortho ethyl toluene, 2,3- dimethyl l-ethyl benzene, 2,4-dimethyl l-ethyl benzene, 2,5-dimethyl l-ethyl benzene, and 2,6- dimethyl l-ethyl benzene to catalytic dehydrogenation so as to produce a correspondin substituted vinyl product and indene compound and separating the indene compound from the reaction products.

2. A process of producin indene and a methyl homolog thereof, by catalytic dehydrogenation which process comprises subjecting a member of the group consisting of ethyl toluenes and ethyl xylenes containing a methyl group adjacent to the ethyl group to catalytic dehydrogenation so as to convert the ethyl compound to the corresponding substituted vinyl compound; and then by urther catalytic dehydrog ion convert-a tion oi the vinyl. material by cross-dehydrogena- :tion with said adjacent methyl group to. thedesired indene material, removing the reaction product from the catalytic dehydrogenation step and separating the indene products from the unreacted ethyl material, recycling said material to the catalytic dehydrogenation step.

4. A process of producing indenes, by catalytic dehydrogenation which process comprises passing through a catalytic dehydrogenation step a member of the group consisting of the ortho toluenes and xylenes which contains a methyl group ortho to the ethyl group, therein dehydrogenating a part of the ethyl material to the corresponding substituted vinyl material and a part by cross-dehydrogenation with said ortho methyl group to the desired indene material, removing the reaction product from the dehydrogenation step and separating unreacted ethyl material and vinyl material from the produced indene and recycling the ethyl material and vinyl material to the dehydrogenation zone.

5. A process of forming an indene, by catalytic dehydrogenation which process comprises subjecting a member of the group consisting of ethyl toluenes and ethyl xylenes which contain a methyl group ortho to the ethyl group to catalytic dehydrogenation so as to first convert a part of the ethyl material to the corresponding substituted vinyl material and to convert a portion of the vinyl material by cross-dehydrogenation with said adjacent methyl group to the desired indene material, removing the reaction product from the dehydrogenation step and separating the indene products from the unreacted ethyl material and recycling said material to the dehydrogenation step, the separation being conducted in a vapor separation step in which the unreacted ethyl material is vaporized under pressure below atmospheric assisted by the introduction of steam while introducing sulphur into said vapor separation zone to inhibit polymerizationof the vinyl material.

6. A process of forming an indene, by catalytic dehydrogenation which process comprises subjecting a member of the group consisting of ethyl toluenes and ethyl xylenes which contain a methyl group ortho to the ethyl group to catalytic dehydrogenation so as to first convert a part of the ethyl material to the corresponding substituted vinyl material and to convert a portion of the vinyl material by cross-dehydrogenation with said adjacent methyl group to the desired indene material, removing the reaction product from the dehydrogenation step and separating the indene products from the unreacted ethyl material and recycling said material to the dehydrogenation step, the separation being conducted in a vapor separation step in which the unreacted ethyl material is vaporized under pressure below atmospheric assisted by the introduction of steam while introducing sulphur into said vapor separation "zone-to inhibitpolymerizatioiiofi the vinyl. ma-

terial, and separating the vinyl material and: re, cycling the same to the dehydrogenation zone.

A process of producing indenes... by catalytic dehydrogenation which process comprises passing through a catalytic dehydrogenation zone ameniber oi the group consisting of ethyl: toluenes and ethyl xylenes having methyl groups ortho tothe ethyl. group, therein dehydrogenating between 15 and 3.5%. of the enteringethyl material so as. to form corresponding substituted vinyl. produots and by cross-dehydrogenation with said ortho methyl group the desiredindenematerial, removing. the reaction mixture from the. dehydrogenation: step and separating theunreacted ethyl material and recycling said material to the dehydrogenation step.

8. A process of producing indenes by catalytic dehydrogenation which comprises passing into a catalytic dehydrogenation zone a member of the group consisting of ethyl toluenes and ethyl xylenes having a methyl group ortho to the ethyl group, therein dehydrogenating between 15% and 35% of the ethyl material to the corresponding substituted vinyl compounds and desired indene material, the indene material being formed by cross-dehydrogenation between the vinyl group and the ortho methyl group, removing the reaction product from the dehydrogenation zone and separating the unreacted ethyl toluenes and ethyl xylenes and vinyl toluenes and vinyl xylenes from the produced indene and recycling such ethyl toluenes and ethyl xylenes and vinyl toluenes and vinyl xylenes to the dehydrogenation zone.

9. A process of producing indenes by catalytic dehydrogenation which comprises passing into a catalytic dehydrogenation zone a member of the group consisting of ethyl toluenes and ethyl xylenes having a methyl group ortho to the ethyl group, therein catalytically dehydrogenating a part of the ethyl material by contact with the catalyst to produce in part the corresponding substituted vinyl material and in part by crossdehydrogenation of the ortho methyl group the indene material and separating the indene material from the reaction products by distillation.

10. A process of producing indenes by catalytic dehydrogenation which comprises passing into a catalytic dehydrogenation zone a member of the grou consisting of ethyl toluenes and ethyl xylenes having a methyl group ortho to the ethyl group, therein catalytically dehydrogenating a part of the ethyl material by contact with the catalyst to produce in part the corresponding substituted vinyl material and in part by cross dehydrogenation of the ortho methyl group the indene material and separating the indene material from the reaction products, the catalyst employed being a chromium oxide catalyst.

- 11. A process of producing indenes by catalytic dehydrogenation which comprises passing into a catalytic dehydrogenation zone a member of the group consisting of ethyl toluenes and ethyl xylenes having a methyl group ortho to the ethyl group, therein catalytically dehydrogenating at a temperature of about 1200-l300 F. a part of the ethyl material by contact with the catalyst to produce in part the corresponding substituted vinyl material and in part by cross-dehydrogenation of the ortho methyl group the indene material and separating the indene material from the reaction products by distillation, the catalyst employed being an admixture of iron oxide, magnesium oxide, and potash, and introducing steam into the dehydrogenation zone for activating the catalyst.

, 12. A process of producing indenes by catalytic dehydrogenation which comprises passing into a catalytic dehydrogenation zone a member of the group consisting of ethyl toluenes and ethyl xylenes having a methyl group ortho to the ethyl group, therein catalytically dehydrogenating at a temperature of about 10001300 F. a part of the ethyl material by contact with the catalyst -to produce in part the corresponding substituted vinyl material and in part by cross-dehydrogenation of the ortho methyl group the indene matehydrogenation zone and separating the iiidene material from the reaction products loy distillation.

WILLIAM E. ELWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS m Number Name Date 1,541,175 Ostromislensky et al. June 9, 1925 1,552,874 Ostromislensky et al. Sept. 8, 1925 2,110,829 Dreisbach Mar. 8, 1938 2,188,772 Dreisbach et al. Jan. 30, 1940 2,443,217 Amos et a1. June 15, 1948 

1. A PROCESS OF PRODUCING INDENES AND METHYL HOMOLOGS THEREOF, BY CATALYTIC DEHYDROGENATION WHICH PROCESS COMPRISES SUBJECTING A MEMBER OF THE GROUP CONSISTING OR ORTHO ETHYL TOLUENE, 2,3DIMETHYL 1-ETHYL BENZENE, 2,4-DIMETHYL 1-ETHYL BENZENE, 2,5-DIMETHYL 1-ETHYL BENZENE, AND 2,6DIMETHYL 1-ETHYL BENZENE TO CATALYTIC DEHYDROGENATION SO AS TO PRODUCE A CORRESPONDING SUBSTITUTED VINYL PRODUCT AND INDENE COMPOUND AND SEPARATING THE INDENE COMPOUND FROM THE REACTION PRODUCTS. 